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Cisco WAN Manager User’s Guide
Version 10.5, Part Number 78-12945-01 Rev. D0, August 2003
Chapter11 CWM to CWM Communications
Degrade Mode
Degrade Mode
The user is able to continue the provisioning of network data, even when communications between a
Primary CWM and Secondary CWM have been interrupted. If for any reason the communications
between CWM servers are interrupted, user data provisioning will be suspended on the Secondary
CWM, but user data provi si oni ng wi ll cont i nue o n t he Pr ima ry CWM. Du rin g that t ime, th e pro v isi on ing
of user data and monitoring of the network are not impacted. This is called the Degraded Mode of
Operation.
In order to provide CWM to CW M communications, a CWM wo rks ta ti on mu st be able to determine,
transparently to the network, if another CWM workstation is currently running in the network. This
requires IP connec tivi ty b etween all CWM workst ations. If all Seconda ry CWMs have lost IP
connectivity with the Primary CWM, then all Secondary CWMs will function in the degraded mode of
operation.
Degrade mode is defined by a loss o f co nnec tivity between the Primary CWM a nd any Secondary
CWMs, in which all Secondary CWMs are unabl e to pro vi si on use r da ta, incl udi ng the ad ding, de leti ng ,
or modifying of user data, w hi le w ait in g fo r a co nn ec tion with the Primary CWM to be r e st or e d. In the
degrade mode a Secondary CWM can still manage the network data (not user data), and provisioning of
network data can still pr oc eed.
Interruption in comm unications between C W M s m a y be due to some of the f ol lowi ng failures:
• Failure Detection
•Unexpected Exit of the Primary C W M G ateway
•Unexpected Exit of the Secondary C WM G at eway
•Primary CWM has lost IP or physical connectivity to all Secondary CWMs
•One Secondary CWM has lo st I P c on n ect ivity w i th th e Primary CWM
•The CWMGateway process dies on th e P rim ary CWM and is not re-started by watchdog.
•The CWM workstation crashed or was power ed o ff
•Primary CWM has lost IP or physical connectivity with the only Secondary CWM in a domain
•Loss of Heartbeat from Primary C WMGateway
Recovering From Degrade Mode

Failure Detection

The failure recovery sce nario involves handling the unexpected death of e it he r the Primary
CWMGateway or a Secondary CWM G a teway as we ll as handling the loss of IP connec tivity between
the Primary and Secondary CW M Gateway s. Note, that the CWMGateway process w i ll be launched by
watchdog, so that it can be automatically restarted i f it dies unexpectedly. Also, an Orbix- s p ec ific
callback mechanism (CORBA::IT _I O Ca ll ba ck ) w o ul d be use d to indicate any break in conn ect ion
between the Primary CWMGat eway an d th e Se condary CWMGateway processes. Th is wi ll enable all
Secondary CWMGateway processes to d et ect w he never th e Primary CWMGateway dies unexpectedl y
and vice versa. Loss of a heartbea t m e ssag e f r o m th e Primary CWMGateway in two consecut ive
heartbeat intervals will indicat e a lo s s o f I P co n nec tivi ty.